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What would be the most efficient way in thoery to build an induction cooker (hob) to run from DC power at low (ish?*) voltages? I say in theory, so the answers are not limited by products that exist on the market, but by the practical physics/engineering (and in case anyone is listening, and wants to bring a specialised cooker to market for Yachts, RVs, off-grid installations etc).

So, asssuming that an inverter to step up the 48V DC to 240V AC would work (if it has enough rated power) but has some inneficiency/loss, could an induction cooker be designed that runs natively on 48V DC source (or 24V) more efficiently?

For context, increasingly sailing yachts are moving to electric only power[1][2][3], with big battery banks and no engine. These systems seem to run at around 48V DC (various other voltages are also used). However, as far as I can tell all induction hobs run on AC domestic power (240/250v AC - or 110V AC in the US I assume). Anecdotally, some of these boats also use electric cooking, so they do not to have to carry gas for the cookers, but I didn't find details of these cooking set ups.

Off-topic for this question is the batteries, their storage capacity and current/power availability. Let's just assume there's plenty. (it's an interesting topic, but it's not what I'm asking here).

* I say low voltage, I don't know if 48V counts or not. It's a far cry from 3V inputs in a microcontroller, but equally far from the multi-kV of high voltage systems.

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  • \$\begingroup\$ There are hobby type induction furnaces at 12 or 24V already. One of these may be a starting point for adapting a design to cooking applications. I'm also interested, also for a small yacht. \$\endgroup\$
    – user16324
    Aug 17, 2020 at 13:25
  • \$\begingroup\$ Use an American one. They're only 120VAC and typically only 1000-1200W. \$\endgroup\$ Aug 21, 2020 at 6:36

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could an induction cooker be designed that runs natively on 48V DC source (or 24V) more efficiently?

A simple block diagram suggests that it can run from DC: -

enter image description here

Picture from here.

At the top left is the incoming AC that is bridge rectified and filtered to provide a DC bus for the main power circuits of the cooker. The bridge rectifier and filter will have losses so, if those are bypassed by using a DC supply that suits the bus voltage then the solution would be more efficient.

Can it be made to work from 48 volts or 24 volts? 

The higher voltage is better because the current would be less for a given power and cable losses would therefore be less. But remember, the coil in the element would need redesigning to suit a lower DC bus voltage because on AC cookers, the bus voltage is going to be roughly in the range 140 volts DC and 350 volts DC (suiting an AC line voltage range of 100 volts RMS to 240 volts RMS). It's doable.

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  • \$\begingroup\$ The step converter@ 1800W will cost more than the resonant cooker doable but at non consumer prices. \$\endgroup\$ Aug 17, 2020 at 14:32
  • \$\begingroup\$ What step converter are you talking about? \$\endgroup\$
    – Andy aka
    Aug 17, 2020 at 14:41
  • \$\begingroup\$ 24 or 48V to 350Vdc 1800W \$\endgroup\$ Aug 17, 2020 at 17:26
  • \$\begingroup\$ I said in my answer that "the coil in the element would need redesigning to suit a lower DC bus voltage". \$\endgroup\$
    – Andy aka
    Aug 17, 2020 at 18:00
  • \$\begingroup\$ yes so 48V with 20A avg and then Pk current plus rms current ripple =?€ ? Cheaper to buy an AC inverter and Stove top and not risk EMI radiation at 50kHz. Or 150kHz for ALUm pots \$\endgroup\$ Aug 17, 2020 at 18:13
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It would need a step up converter, i.e from 12V to something like 400VDC, since there would be lower loss than swiching a very high current on low voltage. Personally I would still use a gas burner, because it stores more energy density VS. Volume/Weight/Price than any battery. And this is not a neglible aspect for a boat.

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  • \$\begingroup\$ Yes with switching currents for 1800W at 80A x2. Never! \$\endgroup\$ Aug 17, 2020 at 14:09
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Well an inverter adds its own resonant circuits, transformers, etc, etc. Seems to me if you have 48V from a decent 100A battery that a well designed boost/buck converter to 480V would be more efficient than 48VDC -> 400VDC -> 240VAC -> 400VDC (or whatever the inductive element wants).

The direct solution would be smaller, and far lighter too.

I expect that if you can design a 12V to 12V transformerless inverter, or even 12V-240V transformerless inverter, that a similar DC-DC converter would also be possible, cheaper, lighter and more efficient. Just eliminate the superfluous conversione to AC.

Would be an interesting thing to work out because a 48V induction burner for offgrid would be very popular. Sounds like it needs a kickstarter for some clever young power engineer.

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Then resonant tank voltage drop detects a load and no load auto cutoff to driver is added with alert indicator. Converting an existing portable cooker is cheaper if you can determine DC voltage used is feasible to create at power levels required .

Mine is 1800W so I strongly suggest you buy a 2kW inverter or use the one you have.

This is not going to be cheap with ripple cap current rating at 48V!!!

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Yes, it's doable. But, the coil needs to to be wounded with VERY heavy wire, capacitors needs to be extremely low ESR, many in parallel; currents will be in a range of 30-50 amps for 1500-2500w, so, because heating loss is proportional with current SQUARED, the amps are a hard problem at low voltage. The coil, for example, its not enough to use 5 times the crossection of the wire used at 230V, let's say not 16 times but 8-10 times CSA plus a good ventilation will suffice

MOSFETS are no problem, since in the last years very powerful MOSFETS at low voltages appeared on the market

NO IGBTs.

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